The present invention relates to a motor vehicle comprising an engine and control devices that are arranged to control a transmission that is driven by the engine.
The invention also relates to a method for controlling the vehicle's transmission comprising the determination of the vehicle's resistance to travel.
The invention also relates to a computer program for carrying out the said method.
In vehicles with automatic planetary gearing-based gearboxes with torque-converter or automatic stepping gearboxes, it is important to use as accurate an estimation as possible of the vehicle's resistance to travel—in order to be able to provide optimal gear changing regimes according to certain given criteria, such as, for example, low fuel consumption or high average speed.
A disadvantage of the known technology is the difficulty of controlling the transmission automatically when the vehicle is being driven in changing environments. For example, the weather can cause changes in the characteristics of the surface on which the vehicle is being driven, or the vehicle's speed or external wind can cause a reduction in the accuracy in implementing a predetermined gear change strategy.
U.S. Pat. No. 4,941,365 describes a system for calculating the resistance to travel, where the acceleration is calculated by measuring the speed on two occasions with the clutch disconnected.
It is desirable to provide a motor vehicle in which a better estimation of the vehicle's resistance to travel is obtained.
It is desirable to obtain in a cost-effective way a better basis for controlling the transmission.
According to an aspect of the present invention, an engine driven vehicle comprises at least an engine, control devices arranged to control a transmission driven by the engine, which control devices are arranged to receive at least two sets of data, each set comprising at least one of a first signal that comprises information about the gradient of the surface on which the vehicle is being driven sent from a first sensor, and at least one second signal that comprises information about the vehicle's speed sent from a second sensor, and at least one third signal that comprises information about the vehicle's acceleration, characterized in that the control devices are also arranged to calculate at least one of two different resistance to travel constants k1 and k2, where k1 is a rolling resistance constant and k2 is an air resistance constant; in response to the first, second and third signals, and to control the transmission in response to at least one of the constants k1 and k2.
A third sensor is preferably arranged to send the third signal. Alternatively, the control devices are arranged to calculate and send the third signal in response to the second signal. Each of the two sets of data is preferably different and each is provided with a unique time stamp.
At least one of the constants is preferably calculated by solving a system of equations, which system of equations comprises the two sets of data.
The information in each of the two sets of data preferably represents values for when the vehicle's propulsive force is 0 (zero).
The said calculation is preferably carried out in response to predetermined information, which said information comprises acceleration due to gravity and vehicle mass.
In this way, a more reliable gear selection is obtained for control of the transmission, which indirectly provides a number of other advantages, such as increased comfort of the driver, less load on the engine and less wear on the vehicle's transmission.
A more reliable gear selection is obtained in particular in situations where the vehicle's air resistance and rolling resistance are abnormally high, such as at high vehicle speeds, with strong headwinds or on wet surfaces. In particular, a more certain gear selection is obtained according to the invention when the vehicle is being driven at a low speed on a steep gradient or at a high speed on a flat surface.
According to the invention, by utilizing components and sensors that are already in the vehicle, more correct information is obtained that can be used as the basis for making decisions for control of the transmission in a cost-effective way.
In addition, according to the invention, better performance of the vehicle while it is being driven is being driven is obtained, as control of the transmission is based on more correct information. The vehicle can thus, for example, be driven in a more fuel-efficient way.